Message to marathoners: Watch your fluid intake!

The study singled out substantial weight gain while running, long race duration, and a lower body mass index as the primary risk factors for hyponatremia in runners. Researchers suggest that the best way to reduce the frequency and severity of hyponatremia is to inform the greater public about the risk factors.

‘Our findings showed that it was the amount rather than the type of fluid a runner consumed that put them at greatest risk for hyponatremia,’ said Christopher Almond, a lead investigator of the study, and cardiac fellow at Children’s Hospital Boston. Whether the runners consumed water or electrolyte-containing fluid made no difference.

According to co-author David Greenes, if the study’s results were representative of the entire field of runners, approximately 1,900 of the 14,573 finishers of the 2002 Boston Marathon had some degree of hyponatremia, 90 of those having critical levels of hyponatremia. This suggests the problem of over-drinking may be more common than previously believed.

While earlier studies have suggested female gender is an important risk factor for hyponatremia, the Children’s report suggests that gender is not the essential factor. Children’s researchers suspect that differences in body size, race time, and drinking patterns between male and female runners are key factors.